int delete_string(char str[], char ch)
{
    int i, j;
    for (i = j = 0; str[i] != '\0'; i++)
        if (str[i] != ch) //如果不是目标元素，则i指针和j指针一起后移
            str[j++] = str[i];
    str[j] = '\0';
    return 0;
}